USMLE PRACTICE QUESTION OF THE WEEK
Question for September 12, 2025
A 65-year-old man presents with gradually worsening fatigue, exertional dyspnea, and palpitations over 2 months. He has a history of hypertension and chronic kidney disease. Physical examination reveals an irregularly irregular pulse and no murmurs. ECG shows an absence of P waves and irregularly spaced QRS complexes.
Which of the following is the most likely cause of this patient's arrhythmia?
Which of the following is the most likely cause of this patient's arrhythmia?
Correct Answer:
A. Atrial dilation secondary to systemic hypertension
Correct Answer Explanation
This patient's irregularly irregular rhythm, absent P waves, and known hypertension are consistent with atrial fibrillation, often triggered by atrial dilation secondary to systemic hypertension or structural heart disease.
Why These Are Incorrect:
- B. Ventricular automaticity causes ventricular arrhythmias, not atrial fibrillation.
- C. PE causes sinus tachycardia or right heart strain patterns, not classic atrial fibrillation presentation.
- D. SA node dysfunction causes bradyarrhythmia, not chaotic atrial activity.
- E. Thyrotoxicosis can cause AF but this patient lacks hyperthyroid symptoms.